When the harvest of a particular orchard crop occurs, the specific crops on each of thousands of trees become ripe at about the same time. Harvest of these thousands of trees is a time consuming process which must be completed quickly while the crop is optimally ripe, and it is therefore advantageous to create systems that complete the harvesting operations as quickly as possible. The conventional solution for rapidly harvesting tree crops include mechanized tree harvesters which, through conventional electro-hydraulic control systems shake nut and fruit trees to cause the crop of nuts or fruit to drop off of the tree. Such harvesters generally are driven to a location proximate to a tree to be harvested, and a shaker head extends towards the tree. The shaker head generally includes movable jaws with pads that clamp the tree and a motor that powers the shaking process. Different types of trees require different clamping positions on the trunk. Larger trees and trees that have been grafted to a larger rootstock are often clamped higher from the ground, and trees that are leaning are often clamped at an angle. Mechanized harvesters are well known in the art, and are described, for example, in U.S. Pat. Nos. 3,163,458; 3,220,268; 3,221,567; and 3,318,629.
When it is desired that the crop not touch the ground, harvest equipment with catching frames are used. This harvest method typically operates with a pair of harvesters: a shaker-equipped vehicle with a catching frame which operates on one side of a tree and a crop receiving vehicle with a catching frame on the other side of the tree. Both harvest vehicles must propel to and stop at a location alongside each of the trees to be harvested in order to catch the crop.
Operation of a mechanized tree harvester requires skill and stamina, due to repeated starting and stopping the vehicle adjacent to each tree, extending the clamping arm to a proper distance, and shaking each tree for a desired duration. In order to relieve the operator of some of this laborious operation, partial automation systems that use sensors and controls on tree harvesters have been developed. For instance, tree shaking machines with sensors and automation controllers are described in U.S. Pat. Nos. 6,658,834 and 7,757,471, both of which are incorporated by reference herein in their entirety for all purposes.
U.S. Pat. No. 6,658,834 (“the '834 patent”) describes a tree sensing device, mounted upon a harvester and controlled by a conventional electro-hydraulic controller. Shaker head control parameters including a desired pre-determined tree distance are input into a programmable controller. When the harvester is driven to a location next to a tree, the operator initiates an automated tree shaking cycle in which a tree sensor provides signals representative of the distance from the sensor to the tree as input signals to the controller. The controller then calculates a measured distance from the tree to the harvester and compares the measured distance to the predetermined tree distance and provides shaker head control signals to cause the shaker head to move outward towards the tree and halt when the measured distance is equal to or less than the predetermined distance. The control system then provides control signals to the shaker head components to cause the shaker head to clamp the tree, to shake the tree, to unclamp the tree and/or to move the shaker head back to the harvester. Further input signals to the controller include desired engine RPM signals for controlling the engine speed and tree shaking time signals for controlling the duration of the tree shaking.
U.S. Pat. No. 7,757,471 (“the '471 patent”) describes a tree harvester control system which incorporates the sensor and automated shaking process of the '834 patent while automatically steering, propelling, and/or stopping the harvester machine to shake each tree. The system incorporates a programmable controller which calculates the distances from machine to tree and from tree to tree. The controller utilizes the relative tree locations to calculate the angular adjustment needed and turns a steering caster the desired angle in order to point the shaker in the correct direction. The controller then causes the harvester to move to the recalculated position and the cycle then repeats itself.
While the systems described in the '834 patent and the '471 patent sense and determine tree location relative to a harvester, the current system and method provides significant improvements to those harvesters, particularly regarding tree location sensing and determination technology. The above patents discuss several types of tree sensors including lasers and describe using an ultrasonic tree sensor mounted directly on the shaker head. However, years of use and evaluation have shown that tree branches can interfere with an ultrasonic measurement of the tree trunk distance, and the very high vibration of the shaker head exceeds the maximum acceleration most sensors can tolerate, causing inaccurate measurements and reducing the operational life of the sensors. Further, the dusty and unpredictable environment introduces challenges to any sensor used. Because accurate determination of tree locations are important for automated shaking and harvester navigation, there is a need for mechanisms and systems to consistently make accurate tree distance and location calculations.
Due to the above highlighted concerns in the field of agricultural tree harvesting, a need exists for refinements and improvements to tree sensing and location referencing technology. While various implementations of partial harvester automation have been developed, no known system has emerged that encompasses the features hereafter presented in accordance with aspects of the present invention.